title: Histopathological features of in situ vein bypass stenoses.
abstract: OBJECTIVE
  To analyse the histopathological features of in situ vein bypass stenoses.
  
  
  METHODS
  Nineteen specimens of primary (n = 16) or recurrent (n = 3) vein graft stenoses obtained from 17 patients during surgical revision were prepared for light microscopy and immunohistochemical investigation. The median time interval from bypass surgery to stenosis excision was 5 months (range 2-52 months). Twenty-seven saphenous vein segments obtained from patients undergoing primary bypass surgery served as controls.
  
  
  RESULTS
  Graft stenoses were characterised by moderate to severe intimal hyperplasia composed of actin positive but desmin negative cells, interspersed with areas of fibrosis. A single layer of factor VIII positive endothelial cells were identified on the luminal surface. The media, separated from the intima by a poorly defined elastic lamina, usually appeared normal or mildly hyperplastic and consisted of smooth muscle cells, which stained positive for actin as well as for desmin. The adventitia was composed of loose connective tissue in which lymphocytes, plasma cells and giant cells were occasionally seen. Atheromatous material was absent from intragraft lesions, but was observed in one specimen, which was harvested from a proximal anastomotic lesion. The majority of pre-bypass vein segments showed evidence of intimal thickening whereas medial hyperplasia was less common.
  
  
  CONCLUSIONS
  In situ vein bypass stenoses mainly consisted of intimal hyperplasia and varying degrees of fibrosis. Similar but less pronounced morphological changes were found in pre-bypass vein segments. The nature of the actin positive but desmin and factor VIII negative intima cells is uncertain, and further studies are needed to characterise this cell type.
authors.affiliation: Department of Vascular Surgery, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: T G
authors.initials: TG
authors.lastname: Nielsen
authors.forename: H
authors.initials: H
authors.lastname: Laursen
authors.forename: M L
authors.initials: ML
authors.lastname: Grønholdt
authors.forename: T V
authors.initials: TV
authors.lastname: Schroeder
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D003251:Constriction, Pathologic / Q000473:pathology; D005260:Female; D006083:Graft Occlusion, Vascular / Q000473:pathology*; D006801:Humans; D006965:Hyperplasia; D007124:Immunoenzyme Techniques; D008297:Male; D012086:Reoperation; D012501:Saphenous Vein / Q000473:pathology / Q000637:transplantation*; D013997:Time Factors; D017539:Tunica Intima / Q000473:pathology